The long-term objectives of the research project are to elucidate mechanisms of ischemic brain damage and, thereby, to help design procedures and pharmacological agents which can prevent or ameliorate brain damage due to stroke and trauma. The specific aims are to clarify the roles played by preischemic hyperglycemia and by tissue acidosis for the evolution and the severity of the brain damage incurred, particularly for the development of pan-necrosis (infarction). The project has two major parts. In the first, attempts are made to clarify whether or not hyperglycemia aggravates damage by exaggerating intra-and extracellular acidosis, and whether acidosis per se is detrimental. This is achieved by variations of plasma glucose concentration at constant tissue pH in rats with hypoxia- ischemia, and by variations of pH by superimposed, extreme hypercapnia in normo- and hyperglycemic animals subjected to transient ischemia. Extracellular pH is measured by ion selective electrodes and tissue damage is assessed by histopathological techniques after 1 week of recovery. The objective of the other major part of the program is to define the cellular and molecular mechanisms by which hyperglycemia and/or acidosis aggravate ischemic brain damage. The working hypothesis is that aggravation of damage is secondary to iron-catalyzed production of free radicals, and to a derangement of cell calcium metabolism. The former is envisaged to damage microvessels, and the latter neurons and glial cells. Emphasis is laid on calcium and calcium- mediated reactions. In one part of this analysis, it will be explored how hyperglycemia and acidosis affect calcium influx during ischemia, and calcium efflux during recirculation, as measured by extracellular Ca2+ electrodes. Parallel experiments are to be performed on neurons in primary culture with the goal to assess how changes in pH affect calcium transients, and their impact on cell viability.The second part of the analysis focuses on the possibility that agonist- and Ca2+-dependent lipolysis leads to sustained changes in membrane function by down-regulation of protein kinase C. The third part, finally, explores whether hyperglycemia/acidosis depresses post-ischemic protein synthesis, e.g., by an altered phosphorylation of the eukaryotic initiation factor 2, or if the hyperglycemia/acidosis inhibits the expression of mRNAs for immediate early genes, growth factors, and tyrosine kinase receptors, and their protein products.